Introduce new getData method to avoid 64bit limit of getFlags

[karussell]

Open questions

• int getData(int index) or maybe byte getData(int index) or ByteRef getData(int index) like lucene does similar? int getData would be easy to implement and not that bad.
• How to do this with Refactoring to reduce set/getFlags usage #472
• Or should we implement a list of GraphExtension? This would allow more dynamically sized data and optional compression
• Or just a separate DataAccess nicely integrated in GHStorage

See something already in this branch https://github.com/graphhopper/graphhopper/compare/intsref_refactoring

Best would be if we can avoid getData method and use higher level methods instead.

getFlags would be still necessary as it is the only 'column' where reversing is applied (#728)

Not part of this issue is to change the data type long to byte[] in the OSMReader IMO.

[karussell]

This is done via #1447